Atelier Photochimie en Orbite au CNES Paris – 08/11/2011

Earth orbit experiments of the Exobiology Team of CBM in Orleans: history and prospects M. Bertrand, B. Barbier, A. Brack, A. Chabin, F. Westall In the context of the emergence of life on Earth more than four billion years ago, we are particularly interested in the formation and fate of organic molecules synthesized in space and their delivery to the primitive Earth via meteorites, micrometeorites and comets. Since 1994, we have been investigating chemical processes relevant to the physical conditions encountered in the interstellar medium via several space experiments in which prebiotic molecules in vented cells were exposed to solar UV. Two two-week experiments were performed on Foton capsules, Biopan I (Barbier et al., 1998) and Biopan II (Barbier et al., 2001 ; Barbier et al., 2002), and another experiment, Perseus, was exposed on the Mir Station for two years (Boillot et al., 2002). In collaboration with the LISA laboratory in Creteil, we participated in EXPOSE-E experiment (Chabin et al., 2009 ; Rabbow et al., 2009 ; Bertrand et al., submitted) from February 2008 to September 2009 and in the EXPOSE-R experiment from March 2010 to January 2011. The same molecules were also exposed in laboratory conditions at the Cologne DLR Center (Deutsches Zentrum für Luft und Raumfahrt) and at the CBM (Centre de Biophysique moléculaire). Although it is not possible to accurately reproduce space conditions in the laboratory, especially with respect to the whole range of cosmic radiation, ground experiments are very important for helping in the preparation and support of space experiments. The results obtained in laboratories are complementary to those obtained in space and are very useful for interpreting and discussing the results. We are especially interested in amino acids and dipeptides because of their common occurrence in carbonaceous meteorites (Cronin & Pizzarello, 1983 ; Martins et al., 2007) and micrometeorites (Brinton et al., 1998 ; Matrajt et al., 2004), and because of the diversity of their functional groups, an important factor for the formation of macromolecules, such as proteins. We used amino acids that had already been detected in carbonaceous meteorites, i.e. the proteic amino acids, glycine, alanine, valine, aspartic acid, glutamic acid, tyrosine, leucine, as well as the non proteic amino acids, amino isobutyric acid and 2-amino butyric acid; the peptides dialanine, dileucine, the tripeptide Glu-Glu-Glu, and the active esters of glutamic acid and of leucine. The amino acids chosen were exposed to study the effect of the VUV light on the alkyl chain length and the effect of substitution on the α or β-carbon. The peptides were chosen to evaluate the stability of the amide bond, and the active esters in order to study peptide condensation and oligomerization. The effect of mineral surfaces as protection against photolysis in space were examined by the exposure of molecules embedded in meteorite powders (Barbier et al., 1998 ; Boillot et al., 2002). After irradiation in space or in the laboratory, the molecules were extracted, derivatized following chiral (Bertrand et al., 2008) and non-chiral procedures, and analysed by liquid chromatography, electrophoresis, or gas chromatography – mass spectrometry. The results show that resistance to irradiation is a function of the chemical nature of the exposed molecules and of the wavelengths of the UV light. They also demonstrate the protective effect of meteorite powders. The most altered compounds were the dipeptides, aspartic and glutamic acids. The most resistant were the amino acids with an alkyl hydrocarbon chain (glycine, alanine, valine, leucine). The results of the different experiments were compared and discussed in order to better understand the effects of the photochemistry on the organic molecules and on the availability of molecules synthesized in space for the aqueous processes in Earth that produced the macromolecules essential for life. The large differences between the results obtained by laboratory experiments and those in Earth orbit demonstrate that new experiments, such as EXPOSE-R2 and VITRINE, are required to better understand the effects of the photochemistry in Space. Barbier B, Boillot F, Chabin A, Venet M, Buré C, Jacquet R, Bertrand-Urbaniak M, Brack A (2001) Behaviour of amino acids and peptides exposed in earth orbit. In: First European Workshop on Exo/Astro-Biology (ed Publication Es). ESA, Frascatti, pp. 291-294.

Atelier Photochimie en Orbite au CNES Paris – 08/11/2011

Barbier B, Chabin A, Chaput D, Brack A (1998) Photochemical processing of amino acids in Earth orbit. Planetary and Space Science, 46: 391-398. Barbier B, Henin O, Boillot F, Chabin A, Chaput D, Brack A (2002) Exposure of amino acids and derivatives in the Earth orbit. Planetary and Space Science, 50: 353-359. Bertrand M, Chabin A, Brack A, Chaput D, Cottin H, Westall F (submitted) the PROCESS experiment: Exposure of amino acids in the Expose-E experiment on the ISS and in laboratory simulations. Astrobiology. Bertrand M, Chabin A, Brack A, Westall F (2008) Separation of amino acid enantiomers VIA chiral derivatization and non-chiral gas chromatography. Journal of Chromatography A, 1180: 131-137. Boillot F, Chabin A, Buré C, Venet M, Belsky A, Bertrand-Urbaniak M, Delmas A, Brack A, Barbier B (2002) The Perseus exobiology mission on Mir : behaviour of amino acids and peptides in Earth orbit. Origins of Life and Evolution of the Biosphere, 32: 359-385. Brinton Klf, Engrand C, Glavin Dp, Bada Jl, Maurette M (1998) A Search for Extraterrestrial Amino Acids in Carbonaceous Antarctic Micrometeorites. Origins of Life and Evolution of Biospheres, 28: 413-424. Chabin A, Bertrand M, Brack A, Cottin H, Westall F (2009) Exposure of Amino Acids on the International Space Station: EXPOSE-Eutef and EXPOSE-R. Origins of Life and Evolution of Biospheres, 39: 352-353. Cronin Jr, Pizzarello S (1983) Amino acids in meteorites. Advances in Space Research, 3: 5-18. Martins Z, Alexander Cmo, Orzechowska Ge, Fogel Ml, Ehrenfreund P (2007) Indigenous amino acids in primitive CR meteorites. Meteoritics & Planetary Science, 42: 2125-2136. Matrajt G, Pizzarello S, Taylor S, Brownlee D (2004) Concentration and variability of the AIB amino acid in polar micrometeorites: Implications for the exogenous delivery of amino acids to the primitive Earth. Meteoritics & Planetary Science, 39: 1849-1858. Rabbow E, Horneck G, Rettberg P, Schott Ju, Panitz C, L'afflitto A, Von Heise-Rotenburg R, Willnecker R, Baglioni P, Hatton J, Dettmann J, Demets R, Reitz G (2009) EXPOSE, an Astrobiological Exposure Facility on the International Space Station - from Proposal to Flight. Origins of Life and Evolution of Biospheres, 39: 581-598.